The present invention relates to a humectant, antistatic agent, dispersant and film-forming agent containing a polysaccharide as active principle, a preparation process of polysaccharides, and Kliebsiella oxytoca TNM-3 strain. More particularly, it relates to a tyrosinase-inhibitory humectant containing a polysaccharide as active principle, and cosmetic compositions containing said humectant; an antistatic agent containing a polysaccharide with high biodegradability as active principle; a dispersant containing a polysaccharide as active principle and capable of dispersing, to inorganic and oleaginous substances in a quite satisfactory way; a film-forming agent containing a polysaccharide as active principle, which is capable of forming a low-viscosity solution and can contain an antibacterial metal as counter ion, and films having high break elongation property formed by using said film-forming agent; a preparation process of polysaccharides; and polysaccharide-productive Kliebsiella oxytoca TNM-3 strain.
Generally, hyaluronic acid and chitosan have been used as humectant. For instance, Japanese Patent Application Laid-Open (KOKAI) No. 63-156707 discloses a cosmetic composition containing hyaluronic acid having a molecular weight of not less than 2,000,000 as humectant. This humectant is disclosed as having the effect of protecting the skin against the outside stimulus and preventing skin chapping and also contributory to bettering the feeling of use of the cosmetics.
In use of humectant as a cosmetic material, it is required that such humectant has a moisture retention percentage preferably in a range of 10 to 50% under the ordinary environmental conditions with a relative humidity of 40-80%. Such humectant is also required that its moisture retaining ability should be scarcely affected by the change of relative humidity (See Fragrance Journal, special issue No. 9 "Science of Humectant", 1988, pp. 34, etc.).
Kojic acid and arbutin are also known to have a tyrosinase-inhibitory activity and blended in the cosmetic composition as a skin beautifying agent.
However, the humectant comprising hyaluronic acid as a primary principle has the serious defect that its moisture retainability is not stable because it changes depending on the ambient humidity.
Glycerol and sodium pyrrolidonecarboxylate as humactant have also the same defect as hyaluronic acid mentioned above, and further their moisture retention is low under the low humidity conditions, so that their effect is not satisfactory in an environment where the humectant is required to exhibit its maximum performance. Also, because of too high hygroscopicity under the high-humidity conditions like the effect with hyaluronic acid, these humectants may serve for giving a sense of stickiness to the skin of the user of the cosmetics or may rather act to deprive the user's skin moisture.
The humectants comprising chitosan also have the serious defect that their moisture retaining performance is low under a low-humidity condition where high moisture retention is required.
No humectant is known which is credited with tyrosinase-inhibitory activity among the conventional humectants such as hyaluronic acid. On the other hand, a significant moisture retainability is not observed in the conventional skin-beautifying agents such as kojic acid and arbutin.
Antistatic agents, in practical use thereof, are applied on the surfaces of plastic articles or synthetic fibers or incorporated in the materials thereof. However, when a low-molecular weight surfactant is used as antistatic agent, its effect will not last long since it may be easily wiped out with a cloth or washed away.
In view of the above, it is remarkable to the synthetic polymer type antistatic agents such as polyethylene glycol, polyoxyethylenediamine, polyvinylbenzyltrimethylammonium chloride, polydiallyldimethylammonium chloride, sodium polystyrenesulfonate and the like which are capable of keeping effect permanently. However, considering the recently environmental pollution problems, it is pointed out that these polymeric antistatic agents are quite unsatisfactory to biodegradability and safety because of synthetic polymer.
Various types of polysaccharides, which are high-molecular weight compounds, such as dextran, pullulan, curdlan, xanthan gum, gellan gum, hyaluronic acid, etc., are utilized in the fields of medicine, foodstuff, cosmetics, etc. Since these polysaccharides are natural products, they have high safety characteristics, and further since they are biodegradable, the scope of their use is expanding as a material which is well compatible with the global environment and the living things.
Natural polysaccharides can be roughly divided into the three types: those derived from plants, those derived from animals and those derived from microorganisms. Among them, those derived from microorganisms, or so-called microorganism-produced polysaccharides are remarkable from the aspects of supply and productivity, and several studies are under way (such as disclosed in Japanese Patent Application Laid-Open (KOKAI) No. 6-136003). Regarding use for dispersants, xanthan gum, which is a microorganism-produced polysaccharide, is widely utilized in many fields of industry.
The dispersants using xanthan gum as a primary ingredient are poor in dispersibility for the inorganic and oleaginous substances, so that a polysaccharide having better dispersibility for above substances is demanded in the market.
Regarding use of film-forming agents, pullulan, which is microorganism-produced polysaccharide, is widely used in many fields of industry. Xanthan gum and hyaluronic acid are also known to have film-forming properties.
However, the films made by using pullulan has low bleak elongation property. Also, since pullulan is a neutral polysaccharide, it is incapable of containing an antibacterial metal such as silver, copper, zinc, etc., as counter ion of acidic polysaccharides. Therefore it is impossible to produce an antibacterial film from pullulan alone.
Generally, for efficient production of films, it is advantageous to the cost down of film-forming that the film-forming agent is used at the high concentrated solution so as to minimize the amount of water evaporated. However, in the case of the acidic polysaccharides such as xanthan gum and hyaluronic acid which are capable of producing the antibacterial film, it is very difficult to prepare the film at a highly concentrated solution because of extremely high viscosity of the solution of these polysaccharides, so that these polysaccharides are unfavorable for the film-forming agents.
In production of polysaccharides by use of microorganisms, it is desirable to use a microorganism having an extracellular polysaccharide productivity, considering ease of collection and purification of the produced polysaccharide.
As a result of the present inventor's earnest studies, it has been found that certain specific polysaccharides produced by a bacterium belonging to the genus Kliebsiella (1) have a tyrosinase-inhibitory activity in addition to a stabilized moisture retainability and are especially suited for blending in cosmetics; (2) have excellent antistatic properties; (3) have excellent dispersibility for the inorganic and oleaginous substances; and (4) are capable of forming a low-viscosity aqueous solution, can contain an antibacterial metal as counter ion and can form a film having high break elongation property. The present invention has been attained on the basis of these findings.